How can I get my sound card to work with my system? If it helps, CentOS is installed on an external hard drive. I know that CentOS 6 is almost 7 years old, however it's the only version that works well with the program I use it for since CentOS 7 renders the program extremely buggy and nearly non-functional.

VM: The VM sound card is an emulated virtual sound card, and not the real hardware. What's your host OS? If it's windows then virtualbox uses the windows setup/driver. If it's CentOS, then it really shouldn't work.

Non-VM: You have to find which module your card needs and then use modprobe or insmod to load it.